Method of annealing strip in coils



Dec. 27, 1966 D. o. NORRIS 3,294,598

METHOD OF ANNEALING STRIP IN COILS Filed April 21: 1964 INVENTOR. DONALD0. NORRIS A r tarney United States Patent 3,294,598 METHQD 0F ANNEALINGSTRIP IN CiIILS Donald 0. Norris, Rocky River, Ohio, assignor to UnitedStates Steel (Iorporation, a corporation of Delaware Filed Apr. 21,1964, Ser. No. 361,333 4 Claims. (Cl. 148-134) This invention relates toa method of annealing cold rolled steel strip in coils. As used herein,the term strip is not limited to material of any particular Width, andincludes material sometimes referred to as sheet.

Conventional practice in bell or box-annealing steel strip is to heatcoils of the strip to temperatures of at least 1000 F. in an annealingfurnace which contains a suitable non-oxidizing atmosphere. When coilsof cold-rolled strip are annealed in this manner, fine longitudinalscratches often appear on the surface of the strip. Such scratches mayremain visible even after the strip as been temper rolled, formed into afinal product and plated. The scratches probably are caused by relativelongitudinal movement of the coil convolutions as the coil is heated. Acoil does not heat uniformly, but heats first from the more exposedportions at the outside and next to the core. Hence, the more exposedconvolutions expand before the others and loosen to produce relativemovement.

An object of my invention is to provide an improved method of annealingstrip in coils in which I overcome the tendency of the strip to developsurface scratches.

A more specific object is to provide an annealing method in which thecoil convolutions are effectively locked against relative longitudinalmovement to prevent surface scratches, but in a way not to cause damageby abrasion or grain breaks.

In the drawing:

FIGURE 1 is a plan view of a coil of steel strip prepared for annealingin accordance with my invention; and

FIGURE 2 is a side elevational view of the core on which I wind thestrip.

According to my invention, I wind a cold-rolled continuous steel stripunder tension on a core which includes a hollow cylindrical body 12, apair of spacers 13, and a pair of reinforcing bars 14. I form eachspacer of a pipe segment of smaller diameter than the core body. I weldthe spacers to the outside of the core body at diametrically oppositesides. The welds extend along each edge of the spacers, as indicated at15. Before attaching the spacers, I weld the two reinforcing bars 14 toopposite sides of the core body, whereby the central portion of eachspacer bears against the respective reinforcing bar. In a typicalinstallation, the core body 12 has an outside diameter of about 16inches, the spacers 13 are cut from 10 inch pipe, and each spacerencompasses an arc of about 72 of this pipe. It is essential to thesuccessful practice of my invention that I avoid abrupt bends in thestrip, such -as would cause abrasions or grain breaks. Hence it3,294,598 Patented Dec. 27, 1966 is necessary that the spacers eachextend around a substantial arc of the surface of the core body. Afterwinding the strip 10 tightly on the core, I apply conventional steelbinding straps 16.

Next I anneal the coil prepared as just described at a temperature of atleast 1000 F., using conventional equipment. As the convolutions of thecoil at the outside and next to the core heat and expand, thenon-circular shape of the coil effectively locks them against relativelongitudinal movement, and thus overcomes the usual tendency for thesurfaces to develop scratches. The reinforcing bars 14 prevent thespacers 13 from collapsing as they soften at high temperatures.

While I have shown and described only a single embodiment of myinvention, it is apparent that modifications may arise. Therefore, I donot wish to be limited to the disclosure set forth but only by the scopeof the appended claims.

I claim:

1. In an annealing process in which cold-rolled continuous steel stripis wound under tension on a hollow core to form a tight coil, and thecoil and core are heated to an annealing temperature from the outside ofthe coil and from the inside of the core, whereby the convolutions ofthe coil at the outside and next to the core expand first, a method ofpreventing scratching of the strip surface comprising locking theconvolutions of the coil against relative longitudinal movement as theyexpand during heating.

2. In an annealing process in which cold-rolled continuous steel stripis wound under tension on a hollow core to form a tight coil, the coilis bound with straps, and the coil and core are heated to an annealingtemperature from the outside of the coil and from the inside of thecore, whereby the convolutions of the coil at the outside and next tothe core expand first, a method of preventing scratching of the stripsurface comprising shaping the core and coil in a non-circularconfiguration which locks the convolutions of the coil against relativelongitudinal movement as they expand during heating.

3. A method as defined in claim 2 in which the noncircular configurationof the coil avoids abrupt bending of the strip to prevent abrasions andgrain brealksi 4. A method as defined in claim 2 in which the core has acylindrical body and spacers welded to diametrically opposed sidesthereof and extending around a substantial arc of the body to avoidabrupt bending of the strip.

References Cited by the Examiner UNITED STATES PATENTS 1,870,577 8/1932Lamb 148-155 X DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner.

2. IN AN ANNEALING PROCESS IN WHICH COLD-ROLLED CONTINUOUS STEEL STRIPIS WOUND UNDER TENSION ON A HOLLOW CORE TO FORM A TIGHT COIL, THE COILIS BOUND WITH STRAPS, AND THE COIL AND CORE ARE HEATED TO AN ANNEALINGTEMPERATURE FROM THE OUTSIDE OF THE COIL AND FROM THE INSIDE OF THECORE, WHEREBY THE CONVOLUTIONS OF THE COIL AT THE OUTSIDE AND NEXT TOTHE CORE EXPAND FIRST, A METHOD OF PREVENTING